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DJR 48-2B: The Transition in Practice to Reduce Bolus Use in Post-Mastectomy Radiotherapy: A Dosimetric Study of Skin and Subcutaneous Tissue

Course Details

MDCB Credits: 2.50

ARRT Credits: 0.75

Available Until: 4/30/2025

Non-Member Price: $87.50

Member Price: $50.00

Member PLUS Price: $50.00

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Authors: Alexandra Guebert, BASc , Michael Roumeliotis, PhD,,, Che Hsuan David Wu, MD, Karen Long, CMD , Natalie Logie, MD,, Tannis Graham, RTP, Alison Gourley, BSc, Peter Craighead, MD,, Michael Sia, MD,, Sarah Quirk, PhD,,,1

Department of Physics & Astronomy, University of Calgary, Calgary, AB, Canada
Department of Oncology, University of Calgary, Calgary, AB, Canada
Tom Baker Cancer Centre, Calgary, AB, Canada

To inform clinical practice for women receiving post-mastectomy radiotherapy (PMRT), this study demonstrates the dosimetric impact of removing daily bolus on skin and subcutaneous tissue. Two planning strategies were used: clinical field-based (n = 30) and volume-based planning (n = 10). The clinical field- based plans were created with bolus and recalculated without bolus for comparison. The volume-based plans were created with bolus to ensure a minimum target coverage of the chest wall PTV and recalculated without bolus. In each scenario, the dose to superficial structures, including skin (3 mm and 5 mm) and subcutaneous tissue (a 2 mm layer, 3 mm deep from surface) were reported. Additionally, the difference in the clinically evaluated dosimetry to skin and subcutaneous tissue in volume-based plans were recalculated using Acuros (AXB) and compared to the Anisotropic Analytical Algorithm (AAA) algorithm. For all treatment planning strategies, chest wall coverage (V90%) was maintained. As expected, superficial structures demonstrate significant loss in coverage. The largest difference observed in the most superficial 3 mm where V90% coverage is reduced from a mean (± standard deviation) of 95.1% (± 2.8) to 18.9% (± 5.6) for clinical field-based treatments with and without bolus, respectively. For volume-based planning, the subcutaneous tissue maintains a V90% of 90.5% (± 7.0) compared to the clinical field-based planning coverage of 84.4% (± 8.0). In all skin and subcutaneous tissue, the AAA algorithm underestimates the volume of the 90% isodose. Removing bolus results in minimal dosimetric differences in the chest wall and significantly lower skin dose while dose to the subcutaneous tissue is maintained. Unless the skin has disease involvement, the most superficial 3 mm is not considered part of the target volume. The continued use of the AAA algorithm is supported for the PMRT setting.

As of January 1, 2022, ARRT requires CE Credits for Directed Journal Readings to be based on the word count for each article. So, the number of CE Credits for each DJR article will vary for ARRT. For this article, the ARRT CE Credit will be 1 Credit. The MDCB CE Credits will remain at 2.5 Credits. 

ARRT CQR Credit Distribution
Radiation Therapy 2017:
  Prescription and Dose Calculation = 0.75 credits
Radiation Therapy 2022:
  Prescription and Dose Calculation = 0.75 credits